Semantic Web-Based Information Systems: State-of-the-Art ...
Semantic Web-Based Information Systems: State-of-the-Art ...
Semantic Web-Based Information Systems: State-of-the-Art ...
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Bu ld ng Ontology Translat on <strong>Systems</strong><br />
From a human user’s point <strong>of</strong> view, <strong>the</strong> first <strong>Web</strong>ODE definition is more legible; at<br />
first glance, <strong>the</strong> user can see that <strong>the</strong> relation usesTransportMean is defined between<br />
<strong>the</strong> concepts flight and airTransportMean, and that its maximum cardinality is one.<br />
In <strong>the</strong> second case, <strong>the</strong> user must find and interpret <strong>the</strong> four components (<strong>the</strong> ad hoc<br />
relation definition and <strong>the</strong> three formal axioms) to reach <strong>the</strong> same conclusion.<br />
A similar conclusion can be obtained from an application point <strong>of</strong> view. Let us suppose<br />
that we want to populate <strong>the</strong> ontology with an annotation tool. The behavior<br />
<strong>of</strong> <strong>the</strong> annotation tool is different for both definitions. With <strong>the</strong> first definition, <strong>the</strong><br />
annotation tool will easily understand that its user interface cannot give users <strong>the</strong><br />
possibility <strong>of</strong> adding more than one instance <strong>of</strong> <strong>the</strong> relation, and that <strong>the</strong> drop-down<br />
lists used for selecting <strong>the</strong> domain and range <strong>of</strong> a relation instance will show only<br />
direct or indirect instances <strong>of</strong> <strong>the</strong> concepts flight and airTransportMean, respectively.<br />
With <strong>the</strong> second definition, <strong>the</strong> annotation tool will allow creating more than one<br />
relation instance from <strong>the</strong> same instance and will display all <strong>the</strong> ontology instances<br />
in <strong>the</strong> drop-down lists instead <strong>of</strong> just presenting instances <strong>of</strong> flight and airTransport-<br />
Mean, respectively. After that, <strong>the</strong> annotation tool will have to run <strong>the</strong> consistency<br />
checker to detect inconsistencies in <strong>the</strong> ontology.<br />
Relationships.Between.Ontology.Translation.Layers<br />
Figure 5 shows an example <strong>of</strong> a transformation from <strong>the</strong> ontology platform <strong>Web</strong>ODE<br />
to <strong>the</strong> language OWL DL. In this example, we have to transform two ad hoc<br />
relations with <strong>the</strong> same name (usesTransportMean) and with different domains and<br />
ranges (a flight uses an airTransportMean, and a cityBus uses a bus). In OWL DL,<br />
<strong>the</strong> scope <strong>of</strong> an object property is global to <strong>the</strong> ontology, and thus we cannot define<br />
two different object properties with <strong>the</strong> same name. In this example, we show that<br />
translation decisions have to be taken at all layers, and we also show how <strong>the</strong> decision<br />
taken at one layer can influence <strong>the</strong> decisions to be made at <strong>the</strong> o<strong>the</strong>rs, hence<br />
showing <strong>the</strong> complexity <strong>of</strong> this task.<br />
Option 1 is driven by semantics; to preserve semantics in <strong>the</strong> transformation, two<br />
different object properties with different identifiers are defined. Option 2 is driven<br />
by pragmatics; only one object property is defined from both ad hoc relations, since<br />
we assume that <strong>the</strong>y refer to <strong>the</strong> same meaning, but some knowledge is lost in <strong>the</strong><br />
transformation (<strong>the</strong> one related to <strong>the</strong> object property domain and range). Finally,<br />
Option 3 also is driven by pragmatics, with more care on <strong>the</strong> semantics; again, only<br />
one object property is defined, and its domain and range is more restricted than in<br />
Option 2, although we still lose <strong>the</strong> exact correspondence between each domain<br />
and range.<br />
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